Emendation of Xanthobacter flavus as a Motile Species

Abstract

Xiznthobucterfluvus 301T (T = type strain) and other strains, including H4-14, both of which were previously described as nonmotile, were reproducibly motile and peritrichously flagellated during the log phase when they were cultured in medium lacking tricarboxylic acid cycle intermediates. Therefore, the species description is emended to include motility and flagellation. Similarly, Xunthobucter uutotrophicus was found to be flagellated and motile, but this finding was not consistently reproducible and was mainly found with the mutant strain Fe-".Currently, the genus Xanthobacter (10) consists of three species, Xanthobacter autotrophicus (the type species), Xanthobacter flavus, and Xanthobacter agilis. Strains of X . auiotrophicus (11) and X. flavus (3, 5 ) have been described as being nonmotile, whereas strains of X. agilis have been described as being motile (2). X. flavus is the only biotin-tequiring species. Typically, new Xanthobacter isolhtes are classified tentatively into one of the three Xanthobacter species on the basis of motility and biotin requirement (12). Recently, Reding et al. reported that Xanthobacter strains isolated from the roots of rice were motile but differed morphologically and physiologically from strains of X. agilis (7, 8). Meijer et al. have described a Xanthobacter strain, strain 25a, that is motile and requires biotin (6).During routine growth experiments, we observed that X. flavus was motile under certain culture conditions. Motility depended on the growth phase and the carbon source (Table 1). In general, growth in the presence of tricarboxylic acid cycle intermediates produced nonmotile cells, whereas growth on alcohols or transfer of washed cells to medium lacking tricarboxylic acid cycle intermediates resulted in motile cells. Growth on H,-CO,, glutamate, or glutamine also produced nonmotile cells. However, we emphasize the effect of tricarboxylic acid cycle intermediates because agilis. This characteristic has been used to differentiate Xanthobacter species (10). Cells of X. flavus produce large amounts of poly-P-hydroxybutyrate as a carbon reserve (lo), and we assume that this compound serves as a carbon and energy source for flagellum synthesis and motility when cells are incubated in a medium lacking usable carbon. The nitrogen source used (NH,, NO3, or N2) had no effect on motility.When cultures were grown with 0.1% n-propanol as the

Azorhizobium oxalatiphilum sp. nov., and emended description of the genus Azorhizobium

“…Motility of X. aminoxidans DSM 15009 T seems to depend on cultivation and testing conditions. as for X. flavus , which first was described as a non-motile species and for which active locomotion and peritrichous flagella were detected later (Reding et al , 1992). While X. aminoxidans is described as being non-motile, we observed swarming of X. aminoxidans DSM 15009 T in soft agar, and also motile cells when harvested from nutrient agar.…”

16S Ribosomal DNA Sequence Analysis Confirms the Close Relationship between the Genera Xanthobacter, Azorhizobium, and Aquabacter and Reveals a Lack of Phylogenetic Coherence among Xanthobacter Species

“…The genus Xanthobacter consists of three species, Xanthobacter agilis (5), Xanthobacter autotrophicus (23), and Xanthobacter jlavus (6,12,17). These organisms are gram-negative, pleomorphic rods that are able to obtain energy by the oxidation of hydrogen and can fix dinitrogen (22).…”